This paper presents an overview of chaotic pulse trains (CPTs) analyzing techniques in recent years. Many techniques had been used such as time domain analysis, frequency analysis, power spectrum density, wavelet analysis, high-speed camera analysis, VHF interferometer technique, X-ray radiation and the list goes on. It was found that a lot of researchers suggest to interpret CPTs as a types of pulse activity produced during the dart leader activities of subsequent leaders or the superposition of a few regular pulse train produced by dart leader activities. There are several previous studies in both regular and chaotic pulse trains agreed with this suggestion. The characteristic of chaotic pulse trains had also been reviewed in this study. Some authors suggest that when a 'chaotic' component is observed during the subsequent leader activities, high frequency intensity would increase. It is also suggested that the downward dart leader gets a lot of luminosity when it goes together with chaotic pulse trains. The speed of the subsequent leaders (associated with CPTs) had also been discussed in this paper. The power spectrum density may be one of the methods to identify CPTs from another subsequent leaders. Several hypotheses on the origin of the CPTs were proposed. More research and analyses should be done in the future in order to clarify the physical phenomena behind chaotic pulse trains occur in between return strokes or in between cloud flashes.
